1. Field of the invention
The present invention relates to a ceramic composition, particularly to an insulating ceramic composition and a ceramic inductor using the same.
2. Description of the Prior Art
The miniaturization of electronic machines and equipment is generally realized by the use of ceramic substrates on which are mounted electronic parts to constitute electric circuits. Efforts to increase the mounting density further are being directed to the development of multilayer ceramic substrates which contain internal circuits and electronic circuit components, such as capacitors and inductors. The multilayer ceramic substrates are often made of aluminium oxide (alumina). Having a sintering temperature as high as 1500-1600.degree. C., alumina needs a large amount of energy for firing. In addition, alumina necessitates the internal conductors to be made of high-melting materials, such as tungsten and molybdenum, which can endure the firing of the alumina. The result is a high resistance in the internal circuits which limits the current capacity.
There is proposed a material for substrates which sinters at low temperatures in JP-A-4-16551. The ceramic composition composed mainly of SiO.sub.2. The ceramic composition can be fired at comparatively low temperatures ranging from 940.degree. C. to 1000.degree. C., which permits internal conductors to be made of copper. Unfortunately, copper needs a reducing or non-oxidizing firing atmosphere. This disadvantage can be eliminated by replacing copper with silver which is resistant to oxidation in the air at high temperatures. Silver, however, makes it necessary to fire the ceramic composition at temperatures lower than 900.degree. C.